Manufacturing device and method for bimetal composite hollow billet

ABSTRACT

A manufacturing device for a bimetal composite hollow billet, includes a mandrel, a frame, a planetary carrier rotatably disposed on the frame, a plurality of rolls rotatably disposed on the planetary carrier, and disposed around the mandrel, and a bimetallic pipe to be processed is sleeved on the mandrel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119 (a) of ChinesePatent Application No. 201910494890.9 filed on Jun. 10, 2019 in theState Intellectual Property Office of the People's Republic of China,the entire disclosure of which is incorporated herein by reference forall purposes.

BACKGROUND 1. Field

The following description relates to the technical field ofmetallurgical bonding manufacturing of bimetal composite pipes, and inparticular, to a manufacturing device and method for a bimetal compositehollow billet.

2. Description of Related Art

A bimetal composite hollow billet is a pipe composed of two differentmetal materials, with a carbon steel pipe or an alloy steel pipe as abase layer pipe, and cladded or lined with a certain thickness ofspecial alloy on an inner surface or an outer surface. Pipe layers aretightly bonded through various deformation and connection techniques, sothat the two materials are integrally bonded. A general design principleof the pipe is that a base material meets an allowable stress of pipedesign, and a clad layer meets the requirements of various complicatedworking conditions. However, for some special operation scenarios, suchas high temperature and high pressure conditions, two metals withdifferent properties must have a firm metallurgical bond at aninterface. In this way, the two metals can meet many performancerequirements such as high strength, corrosion resistance and hightemperature resistance that a single metal cannot meet, and to ensurethe safety and reliability of the composite pipe used in harshenvironments.

The mechanism of bimetallic cladding is complex. Although experts andscholars have done a lot of research, only a small part of the mechanismhas been revealed at present. The following are some theories studiedand proposed by scholars:

Metal bond theory: Proposed by N.S. Buton from a chemical perspective in1954. Two metals are close to each other, and atoms in them areattracted to each other, thereby promoting metal cladding.

Thin film theory: the cladding property of a bimetallic material dependson the surface state of metallic materials. A surface oxide film and anoil film of double metals are removed for consistent plasticdeformation, and when the double metals are close to a certain rangereferring to an action range of a force between atoms, the double metalscan be bonded.

Energy theory: Proposed by A.II. Simeonov in 1958. The theory believesthat what really promotes the bonding between metals is the energy ofthe metal atoms themselves.

Recrystallization theory: Proposed by L.N. Parkes proposed in 1953.Metals are deformed under the action of a high temperature, and at thesame time, because the deformation causes cold work hardening, latticeatoms on a metal contact surface are recombined to form a common crystalgrain, thereby achieving metal cladding.

Diffusion theory: Proposed by Kazakov in the 1970s. When double metalsare heated to near their melting temperatures, an inter-diffusion layerappears in an area where the double metals contact each other, and it isprecisely the diffusion area that promotes the bonding between thedouble metals.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, a manufacturing device for a bimetal compositehollow billet, includes a mandrel, a frame, a planetary carrierrotatably disposed on the frame, a plurality of rolls rotatably disposedon the planetary carrier, and disposed around the mandrel, and abimetallic pipe to be processed is sleeved on the mandrel.

A roll of the plurality of rolls may include a thread section, aflattening section, and a rounding section that are sequentiallydisposed.

The roll and the mandrel may have a first non-zero angle therebetween.

The thread section may include a tapered thread disposed on an outerwall of the roll.

A larger end of the tapered thread may face the flattening section.

The mandrel may be provided with a guide section protruding outward, theguide section may be parallel to the thread section, and the guidesection may be located directly below the thread section.

A rotation direction of the planetary carrier may be opposite to arotation direction of the plurality of rolls.

The bimetallic pipe may be a preformed bimetallic sleeve pipe blank.

The preformed bimetallic sleeve pipe blank may be manufactured byheating the preformed bimetallic sleeve pipe blank above arecrystallization temperature, sleeving the heated preformed bimetallicsleeve pipe blank on the mandrel, and starting the planetary carrier andthe plurality of rolls for rolling.

The preformed bimetallic sleeve pipe blank may include an external layercomposite pipe and an internal layer base pipe disposed coaxially, and awall thickness of the external layer composite pipe may be 26%-28.4% ofa wall thickness of the internal layer base pipe.

In another general aspect, a manufacturing method for a bimetalcomposite hollow billet, includes: heating a preformed bimetallic sleevepipe blank above a recrystallization temperature; sleeving the heatedpreformed bimetallic sleeve pipe blank on the mandrel; and starting theplanetary carrier and the plurality of rolls for rolling.

The preformed bimetallic sleeve pipe blank may include an external layercomposite pipe and an internal layer base pipe disposed coaxially; awall thickness of the external layer composite pipe may be 26%-28.4% ofa wall thickness of the internal layer base pipe.

The preformed bimetallic sleeve pipe blank may be formed by amanufacturing device including a mandrel, a frame, a planetary carrierrotatably disposed on the frame, a plurality of rolls rotatably disposedon the planetary carrier, and disposed around the mandrel, and thepreformed bimetallic sleeve pipe blank to be processed may be sleeved onthe mandrel.

A roll of the plurality of rolls may include a thread section, aflattening section, and a rounding section that are sequentiallydisposed.

The roll and the mandrel may have a first non-zero angle therebetween.

The thread section may include a tapered thread disposed on an outerwall of the roll.

A larger end of the tapered thread may face the flattening section.

The mandrel may be provided with a guide section protruding outward, theguide section may be parallel to the thread section, and the guidesection may be located directly below the thread section.

A rotation direction of the planetary carrier may be opposite to arotation direction of the plurality of rolls.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of an example of amanufacturing device and method for a bimetal composite hollow billet.

FIG. 2 is a schematic structural diagram of an example of a workingcondition of a manufacturing device and method for a bimetal compositehollow billet.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Existing manufacturing processes of bimetal composite hollow billets aredivided into plastic clad forming and non-plastic clad formingprocesses.

I. Plastic Clad Forming Process

Plastic clad forming is a cladding process that utilizes a local oroverall plastic deformation of a pipe to achieve a close bond between aninternal layer pipe and an external layer pipe.

-   1. There is a gap between the internal layer pipe and the external    layer pipe at the beginning.-   2. Deformation stage of the internal layer pipe: After a loading    pressure is applied to an inner wall of the internal layer pipe, the    wall of the internal layer pipe is radially expanded until an outer    surface of the internal layer pipe is in direct contact with an    inner surface of the external layer pipe and the gap is eliminated.    At this time, no contact pressure occurs, but the internal layer    pipe has met a yield condition.-   3. Cladding stage: As the loading pressure continues to increase, a    loading process of the external layer pipe begins. The external    layer pipe first expands elastically. After the inner surface of the    external layer pipe meets the yield condition, the external layer    pipe is partially plastically expanded to reach a maximum loading    pressure.-   4. Unloading stage: the loading pressure is gradually reduced from    maximum to zero; at this time, the internal pipe and the external    pipe are both in an unloading state. Due to the plastic deformation    of the internal layer pipe in the second stage, when the loading    pressure is completely eliminated, the internal and the external    layer pipes are still in contact, resulting in a residual contact    pressure.

During the plastic cladding process, the internal layer pipe iscompletely plastically deformed, and the external layer pipe is in anelastic deformation state or a partial plastic deformation state. Afterunloading, because a springback amount of the external layer pipe isgreater than a springback amount of the internal layer pipe, theexternal layer pipe clamps the internal layer pipe tightly. Thus, thetwo pipes form an expansion force, that is, a residual contact pressure,thereby achieving a close mechanical bond.

The magnitude of the residual contact pressure depends on the springbackcapacity of the material. Under a high temperature condition, thegreater the amount of plastic deformation between the pipe layers duringthe cladding stage, the easier a diffusion reaction to occur at abonding interface to achieve metallurgical bonding at the interface.

According to different states, plastic clad forming can be divided intocold forming and hot forming processes.

(I) Cold Forming Process

A basic characteristic of the cold forming manufacturing process is thata prefabricated thin-walled clad layer (for example, a stainless steelpipe) is nested into a base layer (for example, a carbon steel pipe).Then, through a mechanical method, the internal layer pipe isplastically deformed to overcome a gap at a bonding interface. At thesame time, the external layer pipe is also deformed with a certainamount of elasticity. When an external force is removed, the elasticdeformation of the external layer pipe is recovered, so that an innerwall of the external layer pipe fits tightly on an outer wall of theinternal layer pipe.

The cold forming process can be divided into an external reducing type(for example, a mechanical drawing method) and an internal expandingtype (for example, spin forming, and hydraulic pressure, etc.).

-   1. In the mechanical drawing method, after an external pipe and an    internal pipe are sleeved, the internal pipe is extruded to deform    plastically during a drawing process through a die with a certain    tapered hole or an extrusion die placed in the internal pipe. A side    of the external pipe is simultaneously elastically deformed and    partially plastically deformed. After the drawing process is    finished, the external pipe is subjected to an internal restoring    force to exert an internal compressive stress on the internal pipe,    so that walls of the internal and external pipes are closely bonded.-   2. The mechanical drawing method is suitable for almost all internal    and external pipe materials, but the bonding strength is not high,    and the pipes are easy to debond at a high temperature. In addition,    a wall thickness of the composite pipe may fluctuate to form a    nodular crack on the surface of the pipe, and as a great friction is    generated during the drawing process, the calculation of a drawing    force is not easy.

(1) Spin Forming Method

At present, the spin forming method is a main process for domesticproduction of composite pipes with a stainless steel internal layerpipe. The spin forming method can produce an internally claddedcomposite pipe with better strength than the mechanical drawing method.Industrial composite pipes with a stainless steel internal clad layerare mainly used in the fields of water supply, heating, gas supply,food, pharmacy, fire protection and central air conditioning. Compositepipes with a corrosion-resistant alloy internal clad layer fabricated bythe spin forming process also have some applications in thepetrochemical industry.

Before spinning, there is a gap between an internal layer pipe and anexternal layer pipe of a stainless steel lined composite pipe. After aspinning die applies a pressure to an inner wall of the internal pipe,the diameter of the internal pipe is expanded radially until an outersurface of the internal pipe just contacts an inner surface of theexternal pipe and the gap is eliminated.

As the spinning die continues to increase the pressure on the internallayer pipe, the pressure is transmitted to the external base pipethrough the internal layer pipe, and the external base pipe begins toexpand radially. Due to the plastic deformation of the internal layerpipe, when the pressure is completely removed, the internal and externalpipes are still in contact to produce a contact pressure. At this time,the external pipe is elastically deformed and returns to an originalstate. The internal and external layers are bonded with a distance of5-25 μ, and are in an interference fit state, with a crisp percussionsound.

The stainless steel lined composite pipe produced by the spin formingmethod has the following characteristics:

-   1) The pipe has high interface strength (compared to the drawing    process), strong extrusion resistance and resonance resistance. The    method greatly reduces the possibility of water pipe leakage caused    by an external force impact, thereby avoiding a large amount of    waste of a water resource due to leakage.-   2) Compared with the drawing process, the wall of the composite pipe    produced by the spin forming method is smooth and uniform, and does    not scale; the diameter is guaranteed, and energy consumption is    low.-   3) The pipe is connected by using a traditional technique, and is    safe, flexible and reliable.-   4) Heat energy loss is reduced; the heat preservation performance of    the stainless steel pipe is 24 times that of a copper material water    pipe, which greatly saves the heat energy loss in hot water    transportation.-   5) Cost-effective: the total cost is only 50% the price of a    thin-walled stainless steel pipe and 20% the price of a copper pipe.

(2) Hydraulic Forming Method

The principle of hydraulic forming is basically the same as theprinciple of spin forming, except that a high-pressure liquid is usedfor exerting a pressure in the pipe instead of rotary extrusion by aspinning tool, as shown in FIG. 1. An internal layer pipe and anexternal layer pipe are expanded together by a water pressure. Becausethe external layer pipe is usually more elastic, after the pressure isreleased, the internal layer pipe is placed under a residual compressivestress, and a safe mechanical interference fit is created between theinternal and external layer pipes.

By comparing the two forming methods, for spin forming, the size of theinternal pressure is difficult to determine, under pressure or overpressure is prone to occur, and multiple spins are likely to causecracking of the internal clad layer. For hydraulic forming, the internalpressure is uniform, and the size can be calculated. In addition, theinner wall surface of the composite pipe produced by hydraulic formingis free from abrasion and damage, and no work hardening occurs.Therefore, hydraulic forming is more excellent. However, the two formingmethods have a common weakness that the internal and external layers areonly mechanically bonded, and will debond and fail due to stressrelaxation under a high-temperature environment, like that occurring indrawing forming.

(3) Adhesion +Hydraulic Forming Method

That is, a special adhesive is used between an external base layer pipeof a mechanical lining and an internal pipe of a corrosion-resistantclad layer based on the original hydraulic forming process, making aninterface of a composite pipe bonded more reliably.

To sum up, the cold forming process mainly has the followingcharacteristics:

Advantage: the production process is relatively simple.

Disadvantages:

-   1) the two metal layers are not metallurgically fused, but only    closely fit relying the cold working of the internal and external    layers; under the condition of an axial force, the internal and    external metal layers are difficult to transmit and balance the    external force;-   2) if the cold-worked composite pipe encounters a high temperature,    the composite pipe will have a tendency to debond, and will fail due    to stress release; and-   3) in applications requiring heat transfer, the heat resistance will    increase significantly due to the gap between the internal and    external metal layers.

Due to the inevitable disadvantages of the cold forming process, theusage environment and application fields of cold-worked pipes arelimited.

(II) Hot Forming Process

The hot forming manufacturing process includes two methods: hot rollingand hot extrusion. The former is mainly applicable to the production ofseamed composite pipes, and the latter is applicable to the productionof seamless composite pipes.

-   (1) Hot rolling forming method of clad sheet

Rolling is a traditional method for preparing clad metals. Hot-rolledcladding is essentially pressure welding. If the amount of deformationis large enough, the pressure applied by a roll will destroy an oxidefilm on a metal surface, bringing surfaces into an atomic contact, andwelding the two surfaces together. Advantages: the method has highproductivity, good quality, and low cost, and can greatly save the lossof a metal material. Therefore, the method is currently a widely usedclad material production technology. Rolled clad sheets account for 90%of total clad sheet output. Hot-rolled clad sheets are often used toproduce straight-welded pipes with a wall thickness of less than 32 mm.Disadvantages: One-time investment is large, and many materialcombinations cannot be achieved by rolling cladding.

-   (2) Hot extrusion forming method

Hot extrusion is generally performed on a bimetallic pipe blank, and iscalled clad extrusion. It is the best method for producing seamlessstainless steel and high-nickel alloy seamless composite pipes.

Clad extrusion has the following advantages: the interface ismetallurgically bonded; the force involved in the extrusion process iscompletely a compressive stress. Therefore, the method is particularlysuitable for the working of a high-alloy metal with poor hot workabilityand low plasticity.

The disadvantage is that because the bonding is determined by thediffusion of an element on the interface in a very short time during theextrusion process, it is often affected by the presence of an oxidefilm. Therefore, clad extrusion is currently limited to cladding betweencarbon steel, stainless steel and high-nickel alloys.

II. Non-Plastic Clad Forming

(1) Overlay welding cladding method

Overlay welding is an earlier method for making clad metals. It is aprocess of depositing a metal layer with a specific property on thesurface of a workpiece by methods such as fusion welding, brazing,thermal spraying, and laser cladding. Overlay welding includes hardoverlay welding and metal spraying. The former refers to the use of amelting technology to deposit another layer of metal on a metal surface,and the latter is to deposit a fine metal particle on a metal surface.Many overlay welding methods can be used to prepare a clad metal, butvarious fusion welding methods account for the largest proportion ofoverlay welding. In the narrow sense, overlay welding refers to fusionwelding.

The main disadvantages of overlay welding for manufacturing compositepipes are: the cost is too high for large-area overlay welding, and thecombination of materials that can be produced is limited to compatiblematerials under fusion welding. For example, two materials with verydifferent melting points cannot be cladded, and materials that produce abrittle intermetallic compound during welding cannot be cladded. Atpresent, it is generally difficult to achieve internal deposition ofpipes with a diameter smaller than 4″.

Advantages: the interface is firmly bonded, and the clad layer can bemade of some difficult-to-deform metal materials.

(2) Explosive cladding method

The explosive cladding process relies on a shock wave generated by theexplosion of an explosive to plastically deform an internal pipe toclose to an external pipe, so as to form a composite pipe. By explosiveforming, a clad layer can be less than 0.2 mm. In addition, explosivewelding can be used to achieve connection of a variety of metals, andsome clad layer materials cannot be achieved by other methods.Advantages: one-time instant forming, simple process, and basically thesame pressure generated by the explosion of the explosive at each point.Disadvantages: Due to the irregularity of an inner surface of a baselayer and an outer surppface of an internal clad layer and theunevenness of a wall thickness, the formed composite pipe has a smallbonded area. The interface is non-diffusively metallurgically bonded.The explosive amount of a long composite pipe is difficult to accuratelydetermine, although the control of explosive amount has a certain impacton the full plastic deformation of the internal liner pipe, and has acertain risk.

(3) Centrifugal casting method

The centrifugal casting method is suitable for manufacturing a compositepipe with a melting point of a lined metal lower than that of anexternal layer metal. A clad layer and a base layer are both made of aliquid metal. First, a molten steel for preparing the external pipe isintroduced into a rotating metal die. The temperature inside the pipe ismonitored during the solidification of the external pipe. When theexternal pipe is solidified and reaches a certain temperature, aninternal layer metal, like a corrosion-resistant alloy, is poured. Inthis way, a bimetal composite hollow billet with a firm metallurgicalbond can be produced. Advantages: An interface is metallurgicallybonded, and the composite pipe has high density, and good slag and gasremoval performance. Disadvantages: The method is limited to as-cast useif there is no subsequent thermal deformation. Due to a coarse as-caststructure, the mechanical properties of each layer of metal cannot befully played. In addition, this method cannot produce a clad steel pipewith a light alloy external layer.

(4) Centrifugal casting+hot extrusion (hot extrusion+cold rolling)method

“Centrifugal casting+hot extrusion” is a short-flow composite pipepreparation method. A clad hollow billet is produced by centrifugalcasting. Then, the clad hollow billet is subjected to the procedures ofheating, hot extrusion or hot extrusion+cold rolling, and a subsequentheat treatment to obtain a final composite pipe. This method effectivelycombines the advantages of the two methods of centrifugal casting andhot extrusion. It shortens the production process, realizes a completemetallurgical bond of a clad interface, and overcome the defects of ametal as-cast structure. Its uniqueness lies in the combination of aprimary industrial material with a high-tech metallurgical process. Aplastic thermal clad technology, for example, centrifugal casting, andhot extrusion, etc. and a cold rolling (or cold drawing) productionmethod are used to obtain a high-quality composite pipe.

(5) Centrifugal thermite method

The centrifugal thermite method is also called a self-propagating hightemperature synthesis (SHS) centrifugation method. The essence of thecentrifugal thermite method is to cause a thermite reaction in acentrifugal force field. The so-called thermite reaction is that a metalaluminum powder and other metal oxide powder are uniformly mixed, andare ignited to cause a very rapid exothermic reaction (MO+Al→M+Al₂O₃+Q).An adiabatic temperature of the reaction can be close to 2727° C. (3000K), so the products are all in a liquid state. Under the action of acentrifugal force, high-density products such as Fe, Cr and Ni areconcentrated near an inner wall of a carbon steel pipe to form aninternal clad layer. Al₂O₃ forms an innermost residue, which is removedby a mechanical method, thereby preparing a bimetal composite steelpipe.

(6) Powder metallurgy method

A powder filled layer is added between a main pipe made of carbon steelor a similar material and a thin-walled metal pipe. The pipes are sealedat both ends with a bottom plate. They are heated at a predeterminedtemperature, and hot-extruded into a clad steel pipe. Finally, thebottom plate and the thin-walled metal pipe are removed by pickling.Depending on the application, a clad layer can be an external layer oran internal layer.

(7) Electromagnetic forming method

The electromagnetic forming process belongs to the field of high-energyworking. It uses a transient high-voltage pulsed magnetic field to forcea metal to plastically deform. When a high-voltage direct currentcharges a high-voltage pulse capacitor and the voltage reaches acritical breakdown voltage of an isolating switch, an isolation gap isbroken down. The capacitor adds all the stored energy to a coil. A verylarge current passes through the coil in a few microseconds, producing astrong pulsed magnetic field in an instant. A pipe metal placed outsidethe coil will induce a current in an opposite direction, and a generatedreverse magnetic flux prevents a magnetic flux from passing through thepipe metal, forcing magnetic field lines to be dense in a gap betweenthe coil and the pipe metal. The dense magnetic field lines have anexpansion property, which makes each part of the surface of the pipemetal subjected to a huge impact pressure to collide with a die oranother pipe within a few microseconds. In this way, a plastic flow iscaused at a bonding interface to form a metallurgical bond.

The electromagnetic forming method has high efficiency and safety, andcan connect two metals with very different properties. However, limitedto its special process, at present, the method is only suitable forprocessing materials with low strength and good electrical conductivity,such as copper and aluminum.

Status of forming methods for metallurgically bonded bimetal compositehollow billets

At present, the commonly used forming methods for metallurgically bondedbimetal composite hollow billets with good overall mechanical propertiesin the industry are generally divided into the following four types:

-   1. Rolling cladding method: A preformed composite pipe blank is    heated above a recrystallization temperature, and the pipe blank is    rolled by using a rolling mill. A plastic deformation occurs in a    cross section of the pipe blank, and under a compressive load, a    bimetallic interface forms a close fit (a sufficient pass reduction    is required). After rolling, the waste heat can diffuse atoms    between double metals, thereby forming a metallurgical bond on the    bimetallic interface (the bimetallic interface should have a large    enough contact area).-   2. Explosive cladding method: A composite pipe is produced by using    an explosive welding and cladding process. Two metals are welded    into one by an explosive which releases energy to form a    metallurgical bond.-   3. Explosive+rolling cladding method: First, a composite pipe blank    with a relatively high thickness is obtained by the explosive    cladding method. Then, different requirements and conditions are    distinguished, and a composite pipe that meets a required wall    thickness is prepared by cold rolling or hot rolling.-   4. Centrifugal casting+rolling clad method: First, a composite pipe    blank in which two metals are metallurgically bonded is obtained by    the centrifugal casting method. Then, a composite pipe is prepared    by a cold rolling or hot rolling procedure, which has no defect in a    cast structure and meets a required wall thickness.

The four cladding methods above all have obvious shortcomings.

To solve the above technical problems, the present disclosure provides amanufacturing device and method for a bimetal composite hollow billet,which can firmly bond internal and external layers of metals, have abonding surface which can bear an axial force, and is clean, free froman oxide layer or a cavity.

To achieve the above objective, the present disclosure provides thefollowing solutions.

The present disclosure provides a manufacturing device and method for abimetal composite hollow billet, including a frame, a planetary carrier,a plurality of rolls and a mandrel, where the planetary carrier isrotatably disposed on the frame; the plurality of rolls are rotatablydisposed on the planetary carrier, and the plurality of rolls aredisposed around the mandrel; a bimetallic pipe to be processed issleeved on the mandrel.

Optionally, a roll includes a thread section, a flattening section, anda rounding section that are sequentially disposed.

Optionally, the roll and the mandrel have a first included angletherebetween.

Optionally, the thread section includes a tapered thread disposed on anouter wall of the roll.

Optionally, a larger end of the tapered thread faces the flatteningsection.

Optionally, the mandrel is provided with a guide section protrudingoutward; the guide section is parallel to the thread section, and theguide section is located directly below the thread section.

Optionally, a rotation direction of the planetary carrier is opposite toa rotation direction of the plurality of rolls.

The present disclosure further discloses a manufacturing method usingthe manufacturing device for a bimetal composite hollow billet,including the following steps:

-   step 1, heating a preformed bimetallic sleeve pipe blank above a    recrystallization temperature;-   step 2, sleeving the heated preformed bimetallic sleeve pipe blank    on the mandrel; and-   step 3, starting the planetary carrier and the plurality of rolls    for rolling.

Optionally, the preformed bimetallic sleeve pipe blank includes anexternal layer composite pipe and an internal layer base pipe disposedcoaxially; a wall thickness of the external layer composite pipe is26%-28.4% of a wall thickness of the internal layer base pipe.

Compared with the prior art, the present disclosure achieves thefollowing technical effects:

In the present disclosure, the manufacturing device and method for abimetal composite hollow billet plastically deform the heated preformedbimetallic sleeve pipe blank through the thread section, form a threadgroove on the surface of the external composite pipe and a bimetallicinterface, cause a secondary plastic deformation under the action of theguide section on the mandrel, then flatten and reduce a diameter of thethread groove in the flattening section of the roll, and re-round by therounding section.

In the present disclosure, the manufacturing method for a bimetalcomposite hollow billet causes a severe plastic deformation of thebimetallic interface, increases a bonded area between metals on theinterface, and promotes the cracking of an oxide layer on the surface ofthe metals on the interface. Under the action of rolling waste heat,metal atoms on the interface diffuse into each other to form a bimetalcomposite hollow billet with a firm metallurgical bond, and then hot orcold rolling is performed to produce different specifications offinished bimetal composite pipes with a reinforced metallurgical bond.

Description of reference numerals: 1. mandrel; 2.roll; 3. rotationdirection of roll; 4. rotation direction of planetary carrier; 5.external layer composite pipe; 6. internal layer base pipe; 7. threadsection; 8. reducing section; 9. flattening section; and 10. roundingsection.

Embodiment 1

As shown in FIG. 1, the present embodiment provides a manufacturingdevice and method for a bimetal composite hollow billet, including aframe, a planetary carrier, a plurality of rolls 2 and a mandrel 1,where the planetary carrier is rotatably disposed on the frame; theplurality of rolls 2 are rotatably disposed on the planetary carrier,and the plurality of rolls 2 are disposed around the mandrel 1; abimetallic pipe to be processed is sleeved on the mandrel 1.

In this specific embodiment, as shown in FIG. 1 to FIG. 2, a roll 2includes a thread section 7, a flattening section 9, and a roundingsection 10 that are sequentially disposed. A reducing section 8 isfurther disposed between the thread section 7 and the flattening section9. The roll 2 and the mandrel 1 have a first included angletherebetween. The thread section 7 includes a tapered thread disposed onan outer wall of the roll 2. A larger end of the tapered thread facesthe flattening section 9. The mandrel 1 is provided with a guide sectionprotruding outward; the guide section is parallel to the thread section7, and the guide section is located directly below the thread section 7.A rotation direction of the planetary carrier is opposite to a rotationdirection of the plurality of rolls 2.

The manufacturing device and method plastically deform a heatedpreformed bimetallic sleeve pipe blank through the thread section 7,form a thread groove on the surface of the external composite pipe and abimetallic interface, cause a secondary plastic deformation under theaction of the guide section on the mandrel 1, then flatten and reduce adiameter of the thread groove in the flattening section 9 of the roll 2,and re-round by the rounding section 10.

Embodiment 2

The present embodiment discloses a manufacturing method for a bimetalcomposite hollow billet, including the following steps:

-   step 1, heat a preformed bimetallic sleeve pipe blank above a    recrystallization temperature;-   step 2, sleeve the heated preformed bimetallic sleeve pipe blank on    a mandrel 1; and-   step 3, start a planetary carrier and a plurality of rolls 2 for    rolling.

The preformed bimetallic sleeve pipe blank includes an external layercomposite pipe 5 and an internal layer base pipe 6 disposed coaxially;in this embodiment, a wall thickness of the external layer compositepipe 5 is 27% of a wall thickness of the internal layer base pipe 6.

The manufacturing method causes a severe plastic deformation of abimetallic interface, increases a bonded area between metals on theinterface, and promotes the cracking of an oxide layer on the surface ofthe metals on the interface. Under the action of rolling waste heat,metal atoms on the interface diffuse into each other to form a bimetalcomposite hollow billet with a firm metallurgical bond, and then hot orcold rolling is performed to produce different specifications offinished bimetal composite pipes with a reinforced metallurgical bond.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. A manufacturing device for a bimetal compositehollow billet, comprising: a mandrel; a frame; a planetary carrierrotatably disposed on the frame; a plurality of rolls rotatably disposedon the planetary carrier, and disposed around the mandrel; and abimetallic pipe to be processed is sleeved on the mandrel.
 2. Themanufacturing device of claim 1, wherein a roll of the plurality ofrolls comprises a thread section, a flattening section, and a roundingsection that are sequentially disposed.
 3. The manufacturing device ofclaim 2, wherein the roll and the mandrel have a first non-zero angletherebetween.
 4. The manufacturing device of claim 2, wherein the threadsection comprises a tapered thread disposed on an outer wall of theroll.
 5. The manufacturing device of claim 4, wherein a larger end ofthe tapered thread faces the flattening section.
 6. The manufacturingdevice of claim 4, wherein the mandrel is provided with a guide sectionprotruding outward, the guide section is parallel to the thread section,and the guide section is located directly below the thread section. 7.The manufacturing device of claim 1, wherein a rotation direction of theplanetary carrier is opposite to a rotation direction of the pluralityof rolls.
 8. The manufacturing device of claim 1, wherein the bimetallicpipe is a preformed bimetallic sleeve pipe blank.
 9. The manufacturingdevice of claim 8, wherein the preformed bimetallic sleeve pipe blank isformed by heating the preformed bimetallic sleeve pipe blank above arecrystallization temperature, sleeving the heated preformed bimetallicsleeve pipe blank on the mandrel, and starting the planetary carrier andthe plurality of rolls for rolling.
 10. The manufacturing device ofclaim 9, wherein the preformed bimetallic sleeve pipe blank comprises:an external layer composite pipe and an internal layer base pipedisposed coaxially; and a wall thickness of the external layer compositepipe is 26%-28.4% of a wall thickness of the internal layer base pipe.11. A manufacturing method for a bimetal composite hollow billet,comprising: heating a preformed bimetallic sleeve pipe blank above arecrystallization temperature; sleeving the heated preformed bimetallicsleeve pipe blank on a mandrel; and starting a planetary carrier and aplurality of rolls for rolling.
 12. The manufacturing method of claim11, wherein the preformed bimetallic sleeve pipe blank comprises anexternal layer composite pipe and an internal layer base pipe disposedcoaxially; and a wall thickness of the external layer composite pipe is26%-28.4% of a wall thickness of the internal layer base pipe.
 13. Themanufacturing method of claim 11, wherein the preformed bimetallicsleeve pipe blank is formed by a manufacturing device, comprising: themandrel; a frame; a planetary carrier rotatably disposed on the frame;the plurality of rolls rotatably disposed on the planetary carrier, anddisposed around the mandrel; and the preformed bimetallic sleeve pipeblank to be processed being sleeved on the mandrel.
 14. Themanufacturing method of claim 13, wherein a roll of the plurality ofrolls comprises a thread section, a flattening section, and a roundingsection that are sequentially disposed.
 15. The manufacturing method ofclaim 14, wherein the roll and the mandrel have a first non-zero angletherebetween.
 16. The manufacturing method of claim 14, wherein thethread section comprises a tapered thread disposed on an outer wall ofthe roll.
 17. The manufacturing method of claim 16, wherein a larger endof the tapered thread faces the flattening section.
 18. Themanufacturing method of claim 16, wherein the mandrel is provided with aguide section protruding outward, the guide section is parallel to thethread section, and the guide section is located directly below thethread section.
 19. The manufacturing method of claim 13, wherein arotation direction of the planetary carrier is opposite to a rotationdirection of the plurality of rolls.